Critical Mass
by eyrianone
Summary: Post Episode - 'Countdown' "I'm . . . I'm in love with you." He replies. It's out there now, acknowledged, this force that binds them, but even the writer in him doesn't know what will happen next.
1. Chapter 1

**Title: **Critical Mass

**Author:** Eyrianone

**Rating:** T

**Spoilers: **Post Countdown, happens lets say a week later.

**Summary:**"I'm . . . I'm in love with you." He replies. It's out there now, acknowledged, this force that binds them, but even the writer in him doesn't know what will happen next.

**Disclaimer:** Nothing of what you recognize is mine, I just can't get Richard Castle out of my head – and I have a cousin whose name is actually Richard Castle – awesome huh?

**Authors Notes:** To any reader of my 'Bones' fiction 'Upside Down' you will get an update this week – promise – this delayed it, but Rick Castle is wonderful, guess I'll take on more than I planned.

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In his heart he's not really surprised when it all boils over, pushing her hard up against the wall he kisses her in a fashion he's only ever written about, in a manner that can only be described as 'devouring'. There doesn't seem to be any way to get her close enough, with her trademark four inch heels she's almost nose to nose with him, but her body is half the size of his strong masculine form, she's slender, lithe but strong beneath his questing hands.

It's been coming since the night of their 'undercover distraction' kiss. Like they cracked the seal on nuclear reactor that night, and now the chain-reaction is finally spiraling out of control. Their chemistry, that instant pull that has been there since the day they met, slowly growing from a simple physical attraction into a magnetic force as their friendship began, grew, became close and finally blossomed into love – at least on his part; and he hopes on hers too. Beckett has always maintained she's the 'one and done' kind, and he wants to be her 'one' more than anything in this life.

She moans suddenly into his mouth and the last rational part of his brain that was aware of where they are flees, she consumes him, every functioning part of him focuses like a laser on her and he hitches her up the wall, her legs immediately going around his waist he lets the full force of his desire for her rule, pushing himself against her so she understands exactly what she's doing to him. His reward is another mewl-like sound from the back of her throat and she breaks from their kiss for one brief heart-stopping moment. Gasping his name once, "Rick", she dives right back into the inferno in search of more.

It's been a rough week for him, leaving her alone at the precinct with Josh, swallowing the invitation he'd been about to utter as he noticed the handsome cardiac surgeon approaching, he'd leaned back against the wall as the elevator doors closed, and sighed brokenly. He didn't want to be alone that night, but with his family safely out of town until the following morning, and Josh . . . Josh still in the picture; he had not been willing to disturb Kate's peace. She was in a relationship, one she wanted to make work, and he knew that his baggage made seeing him in the light he wanted her too – hard at best.

Two failed marriages and years as a famously philandering playboy – an image, a somewhat carefully crafted one, but a picture he knew she believed. Was she ready to learn that it wasn't really who he was, would she ever suddenly see, all by herself that he'd begun to leave that person behind him within months of starting to shadow her.

He's always known that for them to become what he wants them to become she has to realize that loving her has altered him and for her – only for her he can be so much more.

For her he will willingly risk his life, walk into situations he has no training for, watch her back, take a bullet if necessary, get blown up, die of radiation poisoning or freeze to death. For her there is no limit to what he is willing to become, even if this means being patient, being a friend and waiting this relationship of hers out . . . because he knows they belong together, he knows, but she has to know too.

Her hand tangles itself, buries itself in his thick shiny hair, she tugs at his scalp, pulling him in deeper, deeper, molding herself to him. The next moan is his; pulled up from deep inside his chest it rips from him in the milliseconds when their mouths aren't fused. Someone is going to catch them any moment if they don't keep it down, his brain can process this thought, but the pull of her, the heat singing down his veins, and hardening his body is force far to strong to deny.

This is his reality, the universe that he inhabits. That he simply cannot stay away from her, cannot deny her anything she could ask of him, he will give her the world and every part of his soul before his life is through.

Her name is carved on his heart, distractions like his reunion with Gina aside, he's really been hers for so long now that his life before she came along seems a world away entirely, a reality where only Alexis is real, and the man he used to be is a stranger to him in all ways bar the father he remains.

"It's not about the books anymore." He told his mother, the truth is it never really was. It was about Beckett, about the desire she stirred up in him, about the pain he needed to vanquish that clouded her emerald eyes, about the fantasies of her, of them, that became two further best-sellers to add to his impressive resume. It was about the man he suddenly could see in the mirror, the one who would prove he was worthy of woman like her, who would stick like glue – 'always' until she could see that man too.

Her tongue licks along his upper lip and a full-body shudder goes right though him, he desperately wants her naked and beneath him, he's aching and dangerously close to the edge – fully clothed and in an interrogation room.

They should stop, they should talk, this is as wrong as it's oh my God amazingly right and he's trying to clear his head enough to real himself in when she breaks their kiss, tightens her legs around him and he sees by the sheer ecstasy on her beautiful face that she's crashed over that edge, her head thudding against the wall.

Neither hears the door to the room open, but suddenly her name is spoken in a harsh angry tone and Castle knows without looking that this has gone from wrong to really wrong as Kate's eyes focus suddenly and she goes rigid and pales.

"Josh . . ." Her voice is a barely formed whisper, her face distorts in distress, which he feels keenly, 'this' isn't her . . . she's the most honest person he's ever met.

Terrified his blue gaze finds hers; she opens her mouth to speak and for a moment he swears his heart stops beating, dread like a lead weight settles across his chest.

"Castle . . ." She says, and the use of this name, not "Rick" is like an ice-pick into his heart.

"Kate . . . please." He pleads, begging her with ever fiber of his existence to not flee.

"Rick." She relents. "I have to explain . . . I have to go . . . you have to let me." She says.

He nods. Shifting he sets her upon her feet and taking an unsteady breath he forces himself to let go of her, it might be the hardest thing he's ever done, to release her now.

She steps around him on trembling legs, the aftershocks of passion thrumming through her. Hand on the door she turns, head bowed, breathing uneven she finds herself unable to leave him like this.

"Rick." Softly her voice caresses his name, and he turns, guilt and fear and longing and desire written all over the face she's come to love most in the entire world.

"This wasn't your fault . . . what's between us; this is what happens when people live in denial too long. I'm the one involved with someone else; the fault here is mine okay."

"I'm . . . I'm in love with you." He replies.

She musters a smile. "I . . . ditto." She tells him before she tugs the door open and leaves.

Castle sinks down into a chair at the table, shaking hands running through his hair, he wills his body to calm and his heart to stop its frantic racing. It's out there now, acknowledged, this force that binds them, but even the writer in him doesn't know what will happen next.


	2. Chapter 2

**Still don't own anybody you recognize, but I would like to hear from you if you would like chapter three.**

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**Critical Mass - Chapter Two  
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Kate Beckett can move extremely quickly in very high heels when she wants too, but with her legs still wobbly under her, the aftershocks of her encounter with Castle, she can't move quickly enough right now to catch up with Josh before he leaves the twelfth.

She makes it to the street outside only in time to see him speeding away on his black Harley, and she's stranded there for a long time staring at his ever diminishing figure, wondering exactly how this all happened.

The worst part is, though she feels awful, really crappy awful about Josh being hurt by her in this manner, she cannot find any moment in her recollection when she could have prevented what happened in that interrogation room from happening.

This thing between her and Castle, the heat that generates between them, she has never experienced anything like this before; never knew or understood that desire, love, need can become so strong that they sweep away all reason, all sanity before them like a tsunami swallowing everything in their path.

She can see now that this has been coming a while, from the beginning maybe, and that their undercover smooch was merely the spark to dry kindling and a roaring blaze was inevitable from that moment forwards. She can regret hurting Josh, hates that she basically cheated, even if she hasn't slept with Rick . . . yet . . . she came in his arms, lost in his embrace and Josh saw enough . . . but she can't regret the moment, or how her body still feels. . . alive . . . so alive – this feeling is too pure to be touched by regrets.

No-one alive knows her the way Rick Castle does, she's never allowed anyone this close before, she didn't intend to let him this close but she wasn't able to hold him out . . . he's the one.

One and done, just like that.

Staring blindly still up the city street after Josh she sees nothing but Castle's anxious face before her.

"_I . . . I'm in love with you."_

It feels like she's been waiting all her life to hear those words from that man. Her shadow, her partner, the man who walks beside her in all situations, faces down murderers with her, punches out hit-men, defuses bombs for her, has her back . . . always.

Because of that love . . . she sees it now. That into their future he will be, will become anything and everything for her and with her.

"_I wish I had someone who would be there for me, and I could be there for him and we could just dive into it together."_

Wish granted.

Her eyes re-focus. She wants nothing more than to return to the precinct upstairs, bury herself in Castle's strong, comforting embrace and emerge to find what happened with Josh today nothing more than a bad dream, but she isn't the type of person to run away from unpleasantness. Anything that frightens her, any problem or challenge, or apology owed must be faced head-on – it's just who she is.

So Kate flags a taxi, checks her back pants pocket for bills and gives the driver Josh's address, she doesn't look back, she just plows forward.

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Dr. Josh Davidson lets himself into his upper west-side apartment and slams the door behind him, satisfied somewhat when it rattles in its hinges before stilling. He drops his keys on the side table by the door, cringes at the roses waiting in the vase on the dining table – and heads for the kitchen, and a shot of something hard, that burns his throat as he swallows it.

Damn her. And her shadow. And damn his own short-sightedness, he knew, he goddamn well _knew_ there was something between them, he felt it, in his gut, the very first time he met the man at the twelfth and Richard Castle didn't know who he was.

Kate hadn't told him. And that should have told Josh everything – and it did, he just didn't want to believe it because Kate is the kind of woman he's wanted all his life. She's beautiful, independent, tough-as-nails, can kick-your-ass, funny, smart, hard-working and honest.

Well maybe not as honest as he thought - no scratch that, Josh knows she's as honest as the day is long, except about her feelings, her feelings for that millionaire playboy writer.

Josh just doesn't get it.

Sure the man is handsome. Sure he's talented; Josh has read some of his work since he's been dating writer-boy's 'muse' and his novels are complicated, intricately thought out page-turners. You can lose yourself; lose all track of time in a Richard Castle crime-thriller, he can't deny that, but the man is . . . irritating. He's a publicity seeking hedonist from everything Josh has learned about him, it seems impossible a woman like Kate Beckett would fall for someone as shallow as that.

But Josh can't wipe what he witnessed between them this afternoon from his mind. He's never experienced the Kate that Castle held in his arms today. He's never been the recipient of her passions in quite that fashion, never heard her make those desperate hungry sounds. Josh hurls his glass across the kitchen; it hits the tiles and smashes into slivers that litter the floor.

A key turns in the lock of the entrance door and he's un-surprised when Kate walks in, scanning the room like the cop she is for him. Her eyes are dry, he notes idly, her face is calm, but the telling blush that creeps up her neck as he looks at her coldly tells him volumes.

She's sorry, but she isn't here to beg him to forgive her.

Josh breaks the silence first. "How long?" He asks her.

She shakes her head. "Nothing like what you saw has ever happened between Rick and me before."

"_Between 'Rick' and me." Funny, he's so used to her always calling him 'Castle'._

"How could you Katie? After all I've given up in order to be here with you." The outrage, the anger in his voice is raw.

"I'm sorry Josh. I'm sorry for what you saw today. I'm sorry I asked you to stay . . . it wasn't fair of me. Not when the truth is . . ." She pauses.

"What . . . what truth Katherine?"

He sees her fists balled by her sides, watches as she paces one step to the side and back again.

She forces herself to stillness; Josh was there for her when Castle left for the summer, and he remained when she asked him too, so she owes him the truth, even though she knows it will hurt him.

"The truth is I've been falling in love with him, since my mother's murder. At first with his books, then with his face on the rear cover; he was my savior, my friend, my companion before we ever met. He was a fantasy Josh . . . and then he was real. And at first I liked my fantasy Richard Castle far more than the actual one, but he isn't how he seems – the image, the public one, he's so much more than that. The real Rick Castle, my partner, that's the one I love Josh. And he loves me. And I hate that this sounds like I'm making excuses, but what we've been through together recently, it just all became clear and what happened today was as unstoppable as the sun coming up tomorrow morning."

He hates every word he's hearing, but it is the truth . . . it's as clear as her eyes.

There's nothing he can say. Nothing he can do. No way he can stand between them.

"Go Kate." He says, simply turning away. "Be happy."

He hears her place her key on the table by the door, hears it close behind her . . . then silence.


	3. Chapter 3

**I think as a post-ep this is complete the way it is now. Enjoy, and if you do, please let me know.**

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**Critical Mass - Chapter Three.**

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She's in another cab en-route back to the twelfth when her cell phone beeps in her jacket pocket, incoming text message alert. She digs around to locate her phone, somehow already knowing the identity of the person trying to contact her.

'_Are you okay? Are we okay?'_

The message is from Castle, and she hears him asking in her head, tone of voice, inflection, nervous blue eyes included. He's scared, she knows he is, about what happened between them today, how far it went, Josh . . . and all the implications, as scared as she is, but maybe not for the same reasons. If she was betting woman, and she is, she'd guess his number one fear right now is that somehow, out of his presence she's decided to remain with Josh and gone begging the doctor to forgive her for a momentary lapse of judgment – a moment of madness, weakness. Kate herself is scared only because everything she wants sits right within her grasp, and she's terrified that it will, at the last moment, be snatched away. They have to talk – clearly.

'_Where are you?'_

She sends him. There's a pause, then his reply comes.

'_I went home. Come to me . . . talk to me.'_

An impish part of her brain can't resist the innuendo.

'_I already came for you! What more do want?'_

There's a longer pause, and she smiles, part of her scared, most of her giddy.

'_I want everything. I need always. Please come.'_

She gives the cab driver the change of destination, and then sends her answer.

'_On my way, be there soon.'_

She doesn't really expect a reply, but then Castle always does like to have the last word.

'_It won't be soon enough.'_

Her cab drops her outside his building twenty minutes later, she waves and says hello to the buildings doorman – there is more than one obviously, and over the last few years she's met them all at various times.

"Hey there, Ms. Nikki." Fred waves to her with a wink. It's a thing with all the doormen, and for some unknown reason she likes it.

The elevator climbs, far too slowly today, and then she's outside the loft's door and before she can knock the door opens suddenly and she's engulfed in his arms as Castle pulls her to him and holds on tight.

"Hi." He murmurs in her ear.

She wraps her arms around his waist in return, lets her head rest against his broad chest as the scent of his cologne tangles itself in her brain. She breathes him in, so familiar, so comforting, so . . . Castle.

They stand wrapped together in the hallway for a long time, finally she feels him take a deep breath and loosen his hold. He steps back; his arms still around her and he looks down into her face, eyes scanning her expression in search of answers.

"So tell me." He says. "Are you really alright?"

She nods. "Yeah Rick I'm okay." She tells him. Adding, "It's over . . . between me and Josh. I should have ended it a while ago, and I knew that . . . I don't know why I didn't."

He moves to the side, tucking her against him he shepherds her inside the loft and kicks the door closed behind them. Then he steers her towards the kitchen and gets her to take a seat on a stool at the counter.

"One foot in the door still I guess." He says hesitantly, going around into the kitchen he looks back over his shoulder at her as he says this, the furtive glance, through his eyelashes, makes him look like a little boy.

"I guess." She responds.

She watches him move around the kitchen, grinding coffee beans and calmly switching on his ridiculously expensive espresso machine, and a warm glow goes through her as he instinctively does something to make her feel better – something as simple as brewing her coffee. Once it's done he pours her a large mug and one for himself, fixes it just the way he's learned she likes it and hands it over the counter, wrapping her hands around the ceramic.

"Talk to me." He says softly, as he comes around the counter and takes the stool next to her. "You can tell me anything Kate."

She takes a mouthful of coffee, lets the rich taste roll around her tongue and tries to decide where to start. In the end, she starts with a question.

She looks right into eyes, gone dark blue and serious, and she asks him, "Why are you in love with me?"

Richard Castle smiles and it lights up his entire face, his eyes glow with warmth. "There is no single reason Kate. I love the sound of your voice. I love your compassion and your determination. I love that energy inside you that never quits, never accepts failure. I love the way your eyes change color when you're angry, or happy, or sad, or wearing red. I love the way your mind works in concert with mine, how when we're together, when we're on a roll, we speak almost as one mind working, one of us continuing where the other leaves off. I love how you smell, how you kiss, how you tease me. I love your coffee addiction and the way you roll your eyes. I love that I can be myself with you, and that you see _me_ not my persona. I love that you're real, that if I'm lucky enough to have you love me back, it'll be because of _who_ I am, not _what_ I am. It'll be because you want me . . . not the things I can give you."

Beckett finds her eyes filling with tears, there are moments when she forgets, just for a second how good he is with words, he could create a beautiful lie, but she knows he wouldn't, that he couldn't, not with her. She smiles through blurred vision.

"And you do love me back . . . right?" He asks.

She nods. "For everything you really are, for always being there, for making me feel extraordinary, for pulling my pigtails and bringing me back to life. I'm happy when I'm with you Rick . . . I'm at peace."

His smile widens. "So what happens now?"

She finds herself laughing, and he smirks at her, four simple words and a multitude of layers.

"Now?" She clarifies, "Or next?"

"Both. Of course." He retorts.

"I'm not sure." She says. "We see if this really works I suppose, if we can have what we've always had and manage to have a romantic relationship too. Do you believe we can manage to do both, or will one of them suffer?" She asks him.

Castle takes one hand off his coffee mug and reaches out for one of hers. Their fingers entwine and he pulls their joined hands to his mouth, brushing the softest kiss across the back of her hand. Heat flares in her stomach at the seemingly innocent caress, her pupils dilate and her eyes fly to his.

"I think together we can do, and be, and become anything we want Kate. I believe that what we've found can weather anything, whether the challenge comes from without or from within, we can make it. That's what I believe."

"You mean when I have trouble sharing you." She says gently.

He shakes his head. "You'll only have to share me with Alexis, and I know she won't mind."

"I'll have to share you with the world Rick; I won't ask you to stop being you just because I want you to be with me. That's one of the mistakes I made with Josh, I couldn't bear to repeat it. This is too important to me, it matters too much. But it will be a challenge for me Rick; I don't want to live under a public microscope, even if I'm willing to in order to be with you."

"They'll get over you know – the press, the public, once we're an old married couple they'll lose all interest." The sentence comes out of his mouth before he considers how far ahead he's racing, he panics and is about to backtrack when he notices that Kate is only smiling.

"I'm jumping ahead – you were still telling me what happens next . . . and now." He says with chagrin.

She squeezes the hand holding hers. "Next, like I said, we figure out how we make this work, and we take this slowly Rick, as much as I want you . . . and it must be really obvious just how much that is . . . I don't want to jump to ten and miss out on two through nine."

He sighs, overly dramatically. "So what you're saying is that _next_ is dating, but _now_ can't be getting naked in my huge bed and letting me make love to you."

The man is wicked she thinks. Positively, wicked and she really wants to just give in to this incendiary desire that simmers right beneath the surface for the both of them. Knowing each other so well dating seems almost redundant, and yet . . . she wants to let this evolve, with her eyes wide open.

"_Now _is dinner and a movie Rick. A cuddle, maybe a make-out session, and then I go home. Tomorrow I go back to work and if we get a case I'll call you, if not, I'll see you for dinner again . . . are you willing to go at my pace and simply be with me?" She asks him.

He smiles happily, leans in to kiss her, and breathes the word across her lips, "Always."


End file.
